Problem: Simplify the following expression: $ x = \dfrac{r + 7}{8} - 5 $
In order to add expressions, they must have a common denominator. Multiply the second expression by $\dfrac{8}{8}$ $ \dfrac{-5}{1} \times \dfrac{8}{8} = \dfrac{-40}{8} $ Therefore $ x = \dfrac{r + 7}{8} + \dfrac{-40}{8} $ Now the expressions have the same denominator we can simply add the numerators: $x = \dfrac{r + 7 - 40}{8} $ $x = \dfrac{r - 33}{8}$